Linux errno 32 broken pipe

How to prevent errno 32 broken pipe?

Currently I am using an app built in python. When I run it in personal computer, it works without problems.

However, when I move it into a production server. It keeps showing me the error attached as below:.

I’ve done some research and I got the reason that the end user browser stops the connection while the server is still busy sending data.

I wonder why did it happen and what is the root cause that prevents it from running properly in production server, while it works on my personal computer. Any advice is appreciated

5 Answers 5

Your server process has received a SIGPIPE writing to a socket. This usually happens when you write to a socket fully closed on the other (client) side. This might be happening when a client program doesn’t wait till all the data from the server is received and simply closes a socket (using close function).

In a C program you would normally try setting to ignore SIGPIPE signal or setting a dummy signal handler for it. In this case a simple error will be returned when writing to a closed socket. In your case a python seems to throw an exception that can be handled as a premature disconnect of the client.

The broken pipe error usually occurs if your request is blocked or takes too long and after request-side timeout, it’ll close the connection and then, when the respond-side (server) tries to write to the socket, it will throw a pipe broken error.

It depends on how you tested it, and possibly on differences in the TCP stack implementation of the personal computer and the server.

For example, if your sendall always completes immediately (or very quickly) on the personal computer, the connection may simply never have broken during sending. This is very likely if your browser is running on the same machine (since there is no real network latency).

In general, you just need to handle the case where a client disconnects before you’re finished, by handling the exception.

Remember that TCP communications are asynchronous, but this is much more obvious on physically remote connections than on local ones, so conditions like this can be hard to reproduce on a local workstation. Specifically, loopback connections on a single machine are often almost synchronous.

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Broken pipe error with multiprocessing.Queue

In python2.7, multiprocessing.Queue throws a broken error when initialized from inside a function. I am providing a minimal example that reproduces the problem.

throws the below broken pipe error

I am unable to decipher why. It would certainly be strange that we cannot populate Queue objects from inside a function.

3 Answers 3

When You fire up Queue.put(), implicit thread is started to deliver data to a queue. Meanwhile, main application is finished and there is no ending station for the data (queue object is garbage-collected).

I would try this:

join_thread() ensures, all data in the buffer has been flushed. close() must be called before join_thread()

What happens here is that when you call main() , it creates the Queue , put 10 objects in it and ends the function, garbage collecting all of its inside variables and objects, including the Queue . BUT you get this error because you are still trying to send the last number in the Queue .

from the documentation documentation :

«When a process first puts an item on the queue a feeder thread is started which transfers objects from a buffer into the pipe.»

As the put() is made in another Thread, it is not blocking the execution of the script, and allows to ends the main() function before completing the Queue operations.

There should be a way to join the Queue or block execution until the object is put in the Queue , you should take a look in the documentation.

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Why am I getting this [Broken pipe] error?

I’m on Ubuntu 18.04. I’m trying to do a buffer overflow attack.

Here’s the C program I wrote and am trying to attack:

Here’s my Python3 injection script:

I tried 3 methods to pipe the output of inject.py to test :

^ Here it actually made the 2nd $ without my input and I had to ctrl+C out after it froze

^ This one is similar to attempt 1

I believe what I’m doing is similar to the many buffer overflows I’ve seen on YouTube. I’d expected a SegFault but instead got Broken pipe errors.

What am I doing wrong? Why am I getting Broken pipe instead of SegFault s?

Clarification: What I’m asking for is not «How to do a buffer overflow attack?», but rather «Why am I getting the Broken pipe error and how can I fix it?». Since this is a problem with the *nix command line, I believe this is within this community’s scope.

1 Answer 1

You get a «broken pipe» error in the Python program since you are not reading the data outputted by it. Your C program totally ignores its standard input stream, and the stream is closed when test terminates, leaving the Python program trying to write to a pipe that nobody is listening to.

A pipe is also used when you employ a process substitution in bash ( ), which is why you get the same issue there. In these examples, the data is not arriving over standard input, but from a file indicated by the command’s first command line argument. You never open this file.

To fix this, make sure that the C program consumes all input from standard input, or from the pathname indicated by the command’s first argument.

Your current code would not cause a buffer overrun, segmentation fault, or any other error, in your C code.

I’m assuming that you’d like to cause a buffer overrun in the C code somehow. You would do that by reading the data from the Python code into a too small buffer, for example.

By the way, the Python code does not need to be Python, it could be a simple shell command that produces a lot of data, such as the yes utility (possibly piped through head -n 1000 or similar, as in yes A | head -n 1000 ).

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IOError: [Errno 32] Broken pipe when piping: `prog.py | othercmd`

I have a very simple Python 3 script:

But it always says:

I saw on the internet all the complicated ways to fix this, but I copied this code directly, so I think that there is something wrong with the code and not Python’s SIGPIPE.

I am redirecting the output, so if the above script was named «open.py», then my command to run would be:

10 Answers 10

The problem is due to SIGPIPE handling. You can solve this problem using the following code:

Update: As pointed out in the comments, python docs already have a good answer.

See here for background on this solution. Better answer here.

To bring information from the many helpful answers together, with some additional information:

Standard Unix signal SIGPIPE is sent to a process writing to a pipe when there’s no process reading from the pipe (anymore).

• This is not necessarily an error condition; some Unix utilities such as head by design stop reading prematurely from a pipe, once they’ve received enough data.
• Therefore, an easy way to provoke this error is to pipe to head [1] ; e.g.:
  • python -c ‘for x in range(10000): print(x)’ | head -n 1

By default — i.e., if the writing process does not explicitly trap SIGPIPE — the writing process is simply terminated, and its exit code is set to 141 , which is calculated as 128 (to signal termination by signal in general) + 13 ( SIGPIPE ‘s specific signal number).

However, by design Python itself traps SIGPIPE and translates it into a Python BrokenPipeError (Python 3) / IOError (Python 2) instance with errno value errno.EPIPE .

• Note: If you use a Unix emulation environment on Windows, the error may surface differently — see this answer.

If a Python script does not catch the exception, Python outputs error message BrokenPipeError: [Errno 32] Broken pipe (Python 3, possibly twice, with Exception ignored in: ‘ mode=’w’ encoding=’utf-8’> sandwiched in between) / IOError: [Errno 32] Broken pipe (Python 2) and terminates the script with exit code 1 [2] — this is the symptom Johannes (the OP) saw.

Windows considerations ( SIGPIPE is a Unix-only signal)

If your script needs to run directly on Windows too, you may have to conditionally bypass code that references SIGPIPE , as shown in this answer.

If your script runs in a Unix subsystem on Windows, the SIGPIPE signal may surface differently than on Unix — see this answer.

There are two ways to solve this problem:

Generally, it is not advisable to silence this exception, as it may signal a severe error condition, depending on your script’s purpose, such as the receiving end of a network socket unexpectedly closing.

• However, if your script is a command-line utility, where quiet termination may not only be acceptable but preferred so as to play nicely with the standard head utility, for instance, you can abort quietly as follows, using signal.signal() to install the platform’s default signal handler (which behaves as described above), as also shown in akhan’s answer (works in both Python 3 and 2):

• Otherwise, if you want to handle the SIGPIPE-triggered exception yourself (works in both Python 3 and 2, adapted from the docs):

[1] Note that in bash you will by default only see head ‘s exit code — which is 0 — reflected in $? afterwards. Use echo $ to see Python’s exit code.

[2] Curiously, on macOS 10.15.7 (Catalina), with Python 3.9.2 (but not 2.x), I see exit code 120 , but the docs say 1 , and that’s what I also see on Linux.

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[Errno 32] ‘Broken pipe’ when trying to multiprocess #7832

Comments

TrentBrick commented Sep 5, 2018

I am running PyMC3 and it tries to sample my distribution with 4 cores. Every time this results in the above error. When I run this in Jupyter Notebooks instead there is no problem at all. Is there some setting for Spyder that I need to turn on to enable multiprocessing?

I have updated to the most recent versions of Spyder and PyMC3.

The text was updated successfully, but these errors were encountered:

ccordoba12 commented Sep 5, 2018

I guess you’re on Windows, right?

@jnsebgosselin, what’s the trick you used to make multiprocessing work there?

TrentBrick commented Sep 5, 2018

jnsebgosselin commented Sep 10, 2018

I @TrentBrick, could you share a minimal example that reproduce the issue please? That would be much appreciated.

TrentBrick commented Sep 14, 2018

The code I run is below with all the error messages pasted below that. It loads in a datafile from https://xcelab.net/rm/statistical-rethinking/

Like I said runs with no problems in Jupyter Notebooks. It dies when I try to get the trace (last line of the with statement)

`# —— coding: utf-8 ——
«»»
Created on Tue Sep 4 20:58:42 2018

import numpy as np
import matplotlib.pyplot as plt

#for i in range(100):
res = np.random.normal( np.random.normal(0, 10, samples), np.random.uniform(0,10,samples), samples )
plt.hist(res)
plt.show()»’

import os
import pandas as pd
df = pd.read_csv(‘rethinking/data/Howell1.csv’, sep=’;’)
display(df.head())
display(df.info())
display(df.describe())

df2 = df[df.age >=18]

import pymc3 as pm
#print(‘Running on PyMC3 v<>‘.format(pm.version))

X1 = df2.weight
Y = df2.height

np.random.multivariate_normal(np.array(alpha, beta), covariance)`

`Traceback (most recent call last):

File «», line 1, in
runfile(‘C:/Users/fmsft/Rethinking Stats/HW4.py’, wdir=’C:/Users/fmsft/Rethinking Stats’)

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